Wireless network system and network address assigning method

ABSTRACT

A wireless network system and a network address assigning method are provided which are capable of reducing traffic occurring when an network address is assigned to each of communication units making up a tree-structure-type wireless network system.  
     The wireless network system includes a radio-relay station, a radio-relay station connected to the radio-relay station and to another radio-relay station in a wireless manner. The radio-relay station preserves a plurality of network addresses to be assigned to these radio-relay stations, assigns a first network address belonging to the plurality of network addresses to one radio-relay station and an address pool making up the plurality of network addresses collectively to the other radio-relay station. The above radio-relay station preserves the address pool and assigns a second network address belonging to the address pool to a wireless terminal. The radio-relay station does not assign directly the network address to the wireless terminal.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a wireless network system and anetwork address assigning method and more particularly to the wirelessnetwork system and network address assigning method capable ofautomatically assigning a network address to each of communication unitsmaking up a tree- structure-type wireless network system. The presentapplication claims priority of Japanese Patent Application No.2000-313584 filed on Oct. 13, 2000, which is hereby incorporated byreference.

[0003] 2. Description of the Related Art

[0004] A wireless network system is known in which a plurality ofcommunication units are connected with each other in a wireless manner.In such the wireless network system, a network address determineduniquely in a network is assigned to each of the communication units.When the communication units carry out communications with each other inthe network, the communication unit to be operated as a destination unitis identified by the network address.

[0005]FIG. 25 shows a known wireless network system in which a pluralityof communication units is connected, in a wireless manner, to carry outcommunications among child terminals of PHSs (Personal HandyphoneSystems). As shown in FIG. 2b, a plurality of the communication units ismade up of a radio-relay terminating station 101, radio-relay stations102-1 to 102-5, and wireless terminals 103-1 to 103-4.

[0006] The radio-relay terminating station 101 is connected to theradio-relay station 102-1 and to the radio-relay station 102-2. Theradio-relay station 102-1 is connected to the radio-relay station 102-3and to the radio-relay station 102-4. The radio-relay station 102-2 isconnected to the radio-relay station 102-5. The radio-relay station102-3 is connected to the wireless terminal 103-1 and-to the wirelessterminal 103-2. The radio-relay station 102-4 is connected to thewireless terminal 103-3. The radio-relay station 102-5 is connected tothe wireless terminal 103-4.

[0007] Such the wireless network system is regarded as a graph in whicheach of a plurality of the communication units serves as a node and eachof connection relations among them serves as a side. The graph isconstructed so as to be of a tree structure and a path to connect theradio-relay terminating station 101 to one of the wireless terminal103-j (j=1,2,3, and 4) is determined uniquely. Of the communicationunits connected on the path, each of the radio-relay station 102-i(i=1,2) existing on a side of the radio-relay terminating station 101 isdefined as a parent station of each of the radio-relay stations 102-i(i=3,4 and 5) and each of the radio-relay station 102-i (i=3,4 and 5)being connected to each of the parent stations is defined as a childstation. Of the communication units connected on the path, each of thewireless terminals 103-j existing on the side of the radio-relayterminating station 101 is defined as a parent station of each of thewireless terminals 103-j and each of the wireless terminals 103-j beingconnected to each or the parent stations is defined as a child stationof each of the defined parent stations.

[0008] At this point, the wireless terminals 103-j are always childstations of the radio-relay stations 102-i. Each of the radio-relaystations 102-i is the child station of the radio-relay terminatingstation 101 or each of the radio-relay stations 102-i′ (i′≠i) and is theparent station of the radio-relay station 102-i″ (i≠i) or each of thewireless terminals 103-j. The radio-relay terminating station 101 isalways the parent station of the radio-relay station 102-i. Though, inthe example shown in FIG. 25, the radio-relay terminating station 101 isconnected indirectly through the radio-relay station 102-i to thewireless terminal 103-j, the radio-relay terminating station 101 may beconnected directly to the wireless terminals 103-j.

[0009] For example, the radio-relay terminating station 101 is theparent station of the radio-relay station 102-1 and the radio-relaystation 102-1 is the child station of the radio-relay terminatingstation 101. The radio-relay station 102-1 is the parent station of theradio-relay station 102-3 and the radio-relay station 102-3 is the childstation of the radio-relay station 102-1. The radio-relay station 102-3is the parent station of the wireless terminal 103-1 and the wirelessterminal 103-1 is the child station of the radio-relay station 102-3.

[0010] The radio-relay terminating station 101 manages data receivedfrom the child station in a unified way and transmits data addressed toeach of the wireless terminals 103-j to each of the wireless terminals103-j. The radio-relay terminating station 101, when being not connecteddirectly to the wireless terminals 103-j being a destination unit, huntsany child station (radio-relay station 102-i) being connected to thewireless terminal 103-j and transfers the data to the hunted childstation (the radio-relay station 102-i).

[0011] The radio-relay station 102-i transfers data received from thechild station to the parent station and transmits data addressed to thewireless terminal to the wireless terminal. The radio-relay station102-i, when being not connected directly to the wireless terminal 103-jbeing the destination unit, hunts any child station (that is, theradio-relay station 102-i′) being connected to the wireless terminal103-j and transfers data to the child station (that is, to theradio-relay station 102-i′) The wireless terminal 103-j is movable and,by being the child station of the radio-relay station 102-i or theradio-relay terminating station 101, transmits data to the radio-relayterminating station 101 and receives data addressed to the wirelessterminal 103-j.

[0012] In the above wireless network system, the radio-relay terminatingstation 101 has a function of a DHCP (Dynamic Host ConfigurationProtocol) server as disclosed in Japanese Patent Application Laid-openNo. Hei 11-55317 and each of a plurality of communication units in thewireless network system, by carrying out communications with theradio-relay terminating station 101, acquires a network address. At thispoint, the wireless terminal 103-j, when Moving, can change its parentstation and the radio-relay terminating station 101, every time thewireless terminal 103-j moves and changes its parent station, reassignsthe network address to the wireless terminal 103-j that has moved andchanged its parent station.

[0013] In that case, communication data gathers in a concentrated mannerto the radio-relay station 102-i existing near to the radio-relayterminating unit, which causes traffic in the wireless network system toincrease and data transmission efficiency in the entire wireless networksystem to be reduced. Moreover, when the number of the radio-relaystation 102-i to connect the communication unit requesting for thenetwork address with the radio-relay terminating station 101 becomeslarger, time required for the relay of data increases more, thus thetime necessary to assign the network address increases.

[0014] If each of the radio-relay stations 102-i is provided with thefunction of the DHCP server, it is necessary to assign two or morenetwork addresses for every radio-relay station 102-i. Because of this,when the number of the radio-relay station 102-i becomes larger, work inwhich the radio-relay terminating station 101 assigns the networkaddress to each of the radio-relay station 102-i increases more.

SUMMARY OF THE INVENTION

[0015] In view of the above, it is an object of the present invention toprovide a wireless network system and a network address assigning methodcapable of reducing traffic occurring when a network address is assignedto each of communication units making up a tree-structure-type wirelessnetwork system. It is another object of the present invention to providethe wireless network system and the network address assigning methodcapable of achieving easy assignment of the network address. It is stillanother object of the present invention to provide the wireless networksystem and the network address assigning method capable of achievingeasy assignment of the network address even when relations ofconnections among the wireless network systems have been changed. It isstill another object of the present invention to provide the wirelessnetwork system and the network address assigning method capable ofachieving easy assignment of the network address even when connection ofa communication unit making up the wireless network system moves toanother wireless network.

[0016] According to a fist aspect of the present invention, there isprovided a wireless network system including:

[0017] a radio-relay terminating station;

[0018] a radio-relay station being connected to the radio-relayterminating station in a wireless manner;

[0019] a wireless terminal being connected to the radio-relay station ina wireless manner; and

[0020] wherein the radio-relay terminating station preserves a pluralityof network addresses to be assigned to the radio-relay station and tothe wireless terminal, assigns a first network address belonging to theplurality of network addresses to the radio-relay station andcollectively feeds an address pool making up a part of the plurality ofnetwork addresses to the radio-relay station and wherein the radio-relaystation preserves the address pool and assigns a second network addressbelonging to the address pool to the wireless terminal.

[0021] In the above aspect, the radio-relay station may be connectedthrough another radio-relay station to the radio-relay terminatingstation. The radio-relay terminating station does not directly assignthe network address to the radio-relay station. This serves to preventan increase in traffic in the wireless network system.

[0022] In the foregoing, a preferable mode is one that wherein includesan other radio-relay station, wherein the other radio-relay stationpreserves an other address pool being different from the address pooland wherein, when the radio-relay station is connected to the otherradio-relay station, the other radio-relay station assigns a thirdnetwork address belonging to the other address pool to the radio-relaystation.

[0023] In the above aspect, if the radio-relay station is disconnectedto the radio-relay terminating station, the radio-relay station isconnected to an other radio-relay station. With the above configuration,since the radio-relay terminating station does not assign directly thenetwork address to the radio-relay station, the traffic in the wirelessnetwork system does not increase.

[0024] Also, a preferable mode is one wherein the other radio-relaystation is connected to the radio-relay terminating station, the otheraddress pool makes up of a part of the plurality of network addressesand the address pool is not renewed and the second network address isnot renewed.

[0025] With the above configuration, the traffic in the wireless networksystem does not increase.

[0026] Also, a preferable mode is one that wherein includes an otherradio-relay terminating station which preserves an other plurality ofnetwork addresses being different from the plurality of networkaddresses, and wherein, when the other radio-relay station is connectedto the other radio-relay terminating station, the address pool isrenewed to become still an other address pool making up a part of theplurality of the other network addresses and the second network addressis renewed to become a fourth network address belonging to the otheraddress pool.

[0027] In the above aspect, the wireless network constructed for everyradio-relay terminating station. It is preferable that, only when theother radio-relay station is system is connected to an other wirelessnetwork system, the address pool is renewed and the network address ofthe child station of the radio-relay station is renewed.

[0028] According to a second aspect of the present invention, there isprovided a network address assigning method for assigning a networkaddress to a radio-relay station and a wireless terminal in a wirelessnetwork system made up of a radio-relay terminating station, theradio-relay station, and the wireless terminal, the method including:

[0029] a step of feeding a plurality of network addresses to theradio-relay terminating station;

[0030] a step of assigning a first network address belonging to theplurality of network addresses to the radio-relay station beingconnected to the radio-relay terminating station in a wireless manner;

[0031] a step of notifying the radio-relay station being connected tothe radio-relay terminating station in the wireless manner of an addresspool making up a part of the plurality of network addresses; and

[0032] a step of assigning a second network address belonging to theaddress pool to the wireless terminal being connected to the radio-relaystation in a wireless manner.

[0033] In the above aspect, the radio-relay terminating station does notassign directly the network address to the radio-relay station. Thisthus serves to prevent an increase in traffic in the wireless networksystem.

[0034] In the foregoing, a preferable mode is one wherein the wirelessnetwork system includes an other radio-relay station having an otheraddress pool being different from the address pool and wherein, theradio-relay station is connected to the other radio-relay station, athird network address belonging to the other address pool is assigned tothe radio-relay station.

[0035] In the above aspect, the radio-relay terminating station does notdirectly assign the network address to the radio-relay station. Thisserves to prevent the increase in the traffic in the wireless networksystem.

[0036] Also, a preferable mode is one wherein, when the otherradio-relay station is connected to the radio-relay terminating station,the other address pool makes up the plurality of network addresses andthe address pool is not renewed and the third network address is notrenewed.

[0037] With the above configuration, the traffic in the wireless networksystem does not increase.

[0038] Also, a preferable mode is one wherein the wireless networksystem includes an other radio-relay terminating station and wherein,when the other radio-relay station is connected to the other radio-relayterminating station, the network address assigning method comprises:

[0039] a step of feeding plurality of network addresses being differentfrom the an other plurality of network addresses to the otherradio-relay terminating station;

[0040] a step of notifying the other radio-relay station of the otheraddress pool making up a part of the other plurality of networkaddresses;

[0041] a step of notifying the radio-relay station of still an otheraddress pool making up a part of a plurality of other network addresses;and

[0042] a step of assigning a fourth network address belonging to stillan other address pool to the wireless terminal.

[0043] In the above aspect, the wireless network system is constructedfor every radio-relay terminating station. It is preferable that, onlywhen-the radio-relay station is connected to an other wireless networksystem, the address pool that the radio-relay station has is renewed andthe network address of the child station of the radio-relay station isrenewed.

[0044] Furthermore, a preferable mode is one wherein each of theplurality of network addresses contains a value corresponding to theradio-relay terminating station and wherein, when the value belonging tothe first network address is different from the value belonging to thethird network address, still other address pool is notified.

[0045] In the above mode, whether the connection of the radio-relaystation has moved to an other wireless network system is judged based onthe network address assigned to the radio-relay station and, when theconnection of the radio-relay station is judged to have moved, theradio-relay station instructs the radio-relay terminating station to getthe address pool.

[0046] With the above configurations, the network address can beautomatically assigned to each of communication devices making up atree-structure-type wireless network system without increases in thetraffic in the network system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and other objects, advantages, and features of thepresent invention will be more apparent from the following descriptiontaken in conjunction with the accompanying drawings in which:

[0048]FIG. 1 is a schematic block diagram showing a wireless networksystem of an embodiment of the present invention;

[0049]FIG. 2 shows a data structure of a wireless control signal messageemployed in the wireless network system according to the embodiment ofthe present invention;

[0050]FIG. 3 shows a data structure of a participation request messageemployed in the wireless network system according to the embodiment ofthe present invention;

[0051]FIG. 4 shows a data structure of a participation acknowledgmentmessage employed in the wireless network system according to theembodiment of the present invention;

[0052]FIG. 5 shows a data structure of an address acquiring requestmessage employed in the wireless network system according to theembodiment of the present invention;

[0053]FIG. 6 shows a data structure of an address assigning notificationmessage employed in the wireless network system according to theembodiment of the present invention;

[0054]FIG. 7 shows a data structure of an address assigning refusingmessage employed in the wireless network system according to theembodiment of the present invention;

[0055]FIG. 8 shows a data structure of an address pool acquiring requestmessage employed in the wireless network system according to theembodiment of the present invention;

[0056]FIG. 9 shows a data structure of an address pool assigningnotification message employed in the wireless network system accordingto the embodiment of the present invention;

[0057]FIG. 10 shows a data structure of an address assigning refusingmessage employed in the wireless network system according to theembodiment of the present invention;

[0058]FIG. 11 is a flowchart explaining an operation of a radio-relaystation according to the embodiment of the present invention;

[0059]FIG. 12 is a flowchart explaining the operation of the radio-relaystation according to the embodiment of the present invention;

[0060]FIG. 13 is a flowchart explaining the operation of the radio-relaystation according to the embodiment of the present invention;

[0061]FIG. 14 is a flowchart explaining the operation of the radio-relaystation according to the embodiment of the present invention;

[0062]FIG. 15 is a diagram showing sequences of operations required tonewly construct a wireless network system according to the embodiment ofthe present invention;

[0063]FIG. 16 is a diagram showing sequences of operations required tonewly construct the wireless network system according to the embodimentof the present invention;

[0064]FIG. 17 is a block diagram showing another example of the wirelessnetwork system according to the embodiment of the present invention;

[0065]FIG. 18 is a diagram showing operations performed whencommunication between two communication devices making up the wirelessnetwork system of the embodiment becomes impossible;

[0066]FIG. 19 is another continued diagram showing operations performedwhen communication between two communication devices making up thewireless network system of the embodiment becomes impossible;

[0067]FIG. 20 is a diagram showing operations performed whencommunication between the radio-relay station and the wireless terminalof the embodiment becomes impossible;

[0068]FIG. 21 is another continued diagram showing operations performedwhen communication between the radio-relay station and the wirelessterminal of the embodiment becomes impossible;

[0069]FIG. 22 is a block diagram showing another example of the wirelessnetwork system according to the embodiment of the present invention;

[0070]FIG. 23 is a diagram showing operations performed whencommunication between two radio-relay stations of the embodiment becomesimpossible;

[0071]FIG. 24 is another continued diagram showing operations performedwhen communication between the two radio-relay stations of theembodiment becomes impossible; and

[0072]FIG. 25 is a schematic block diagram showing a known conventionalwireless network system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0073] Best modes of carrying out the present invention will hedescribed in further detail using various embodiments with reference tothe accompanying drawings.

Embodiment

[0074]FIG. 1 is a schematic block diagram showing a wireless networksystem of an embodiment of the present invention. In the embodiment, aplurality of communication units is connected in a wireless manner tocarry out communications between child terminals of PHSs. As shown inFIG. 1, the wireless network system includes a radio-relay terminatingstation 1, radio-relay stations 2-1 and 2-2, and wireless terminals 3-1and 3-2. The radio-relay terminating station 1 is connected to theradio-relay station 2-1 and to the radio-relay 2-2. The radio-relaystation 2-1 is connected to the wireless terminal 3-1. The radio-relaystation 2-2 is connected to the wireless terminal 3-2.

[0075] Such the wireless network system can be compared to a graph inwhich each of the plurality of communication units serves as anode andeach of connection relations serves as a side. The graph is soconstructed as to be of a tree structure and a path to connect theradio-relay terminating station 1 to wireless terminal 3-j (j=1, 2, . .. ) is determined uniquely. Of the communication units connected on thepath, the communication unit being connected directly to one ofcommunication units 2-i (i=1, 2, . . . ) and existing on a side of theradio-relay terminating station 1 is defined as a parent station of eachof the radio-relay stations 2-i and each of the radio-relay stations 2-iis defined as a child station of the parent station. Of thecommunication units being connected on the path, the communication unitbeing connected directly to one of the wireless terminations 3-j andexisting on the side of the radio-relay terminating station 1 is definedas a parent station of the wireless terminals 3-j and each of thewireless terminals 3-j is defined as a child station of the parentstation.

[0076] The radio-relay terminating station 1 has an address managingtable 4, an address assigning section 5, an address pool assigningsection 6, an input/output section 7, and a parent station processingsection B. The address managing table 4 stores and manages a pluralityof network addresses to be assigned to each of the radio-relay stations2-i and to each of the wireless terminals 3-j. With reference to FIGS.15 and 16, the address assigning section 5, in response to an addressacquiring request message 50, transmits an address assigningnotification message 54 to its child station.

[0077] The address pool assigning section 6, in response to an addresspool acquiring request message 70, transmits an address pool assigningnotification message 75 to its child station. The input/output section 7transmits and receives date or messages to and from the child station.The parent station processing section 8 transmits intermittently awireless control signal message 30 to the child station and, in responseto a participation request message 34 transmitted from the childstation, transmits a participation acknowledgment message 38.

[0078] Each of the radio-relay stations 2-i includes an input/outputsection 11-i, an address acquiring section 12-i, an address poolacquiring section 13-i, an address managing table 14-i, an addressassigning section 15-i, an input/output section 16-i, a child stationprocessing section 17-i, and a parent station processing section 18-i.The input/output section 11-i transmits and receives data or messages toand from the parent station. The address acquiring section 12-itransmits the address acquiring request message 50 to the parent stationand acquires an assigned address 57 from the address assigningnotification message 54 transmitted from the parent station and storesthe acquired address.

[0079] The address pool acquiring section 13-i transmits the addresspool acquiring request message 70 to the parent station and acquires aplurality of network addresses from the address pool assigningnotification message 75 transmitted from the parent station and storesthe plurality of acquired network addresses in the address managingtable 14-i. The address managing table 14-i stores the plurality of thenetwork addresses to be assigned to the child station of the radio-relaystation 2-i and manages them. The address assigning section 15-i, inresponse to the address acquiring request message 50 transmitted fromthe child station, transmits the address assigning notification message54 to its child station.

[0080] The input/output section 16-i transmits and receives data ormessages to and from the child station. The child station processingsection 17-i receives the wireless control signal message 30 transmittedfrom the parent station and transmits the participation request message34 to the parent station. The parent station processing section 18-itransmits the wireless control signal message 30 to the child stationintermittently and, in response to the participation request message 34,transmits the participation acknowledgment message 38.

[0081] Each of the wireless terminals 3-j has an input/output section21-j, an address acquiring section 22-j, and a child station processingsection 23-j. The input/output section 21-j transmits data or messagesto and from the parent station. The address acquiring section 22-jtransmits the address acquiring request message 30 to the parentstation, acquires an assigned address from the address assigningnotification message 54 transmitted from the parent station and storesthe acquired address. The child station processing section 23-j receivesthe wireless control signal message 30 transmitted from the parentstation and transmits the participation request message 34 to the parentstation.

[0082]FIG. 2 shows a data structure of the wireless control signalmessage 30. The wireless control signal message 30 is made up of amessage code 31, a parent station communication unit ID (identifier) 32and a system code 33. The message code 31 is a code to show that amessage is the wireless control signal message 30. The parent stationcommunication unit ID 32 is the ID used to uniquely identify the parentstation transmitting the wireless control signal message 30 and is setindependently of the network address. The system code 33 is a code usedto identify a wireless network system to which the parent stationtransmitting the wireless control signal message 30 belongs. A codebeing different in every wireless network system is substituted into thesystem code 33 or one code is substituted into a plurality of thewireless network systems.

[0083]FIG. 3 shows a data structure of the participation request message34. The participation request message 34 is made up of a message code35, a parent station communication unit ID 36, and a system code 37. Themessage code 35 is a code to show that a message is the participationrequest message 34. A value of the parent station communication unit ID32 added to the wireless control signal message 30 is substituted as theparent station communication unit ID 36. A value of the system code 33added to the wireless control signal message 30 is substituted as thesystem code 37.

[0084]FIG. 4 shows a data structure of the participation acknowledgmentmessage 38. The participation acknowledgment message 38 is made up of amessage code 39, a parent station communication unit ID 40 and systemcode 41. The message code 39 is a code to show that a message is theparticipation acknowledgment message 38. A value of the parent stationcommunication unit ID 32 added to the wireless control signal message 30is substituted as the parent station communication unit ID 40. Thesystem code 41 is a code used when the parent station identifies thechild station uniquely and is set independently of the network address.During a period from time when the child station receives theparticipation acknowledgment message 38 to time when the child stationacquires the network address, the child station uses the system code 41as the network address.

[0085]FIG. 5 shows a data structure of the address acquiring requestmessage 50. The address acquiring request message 50 is made up of amessage code 51, a communication unit ID 52 and an acquired address 53.The message code 51 is a code to show that a message is the addressacquiring request message 50. The communication unit ID 52 is an ID usedto uniquely identify the child station transmitting the addressacquiring request message 50 and is independent of the network address.When the child station transmitting the address acquiring requestmessage 50 has not yet acquired the network address, a “0” (zero) issubstituted as the acquired address 53 and when the child station hasalready the network address, the acquired network address is substitutedas the acquired address 53.

[0086]FIG. 6 shows a data structure of the address assigningnotification message 54. The address assigning notification message 54is made up of a message code 55, a communication unit ID 56, an assignedaddress 57, and an assigned period 58. The message code 55 is a code toshow that a message is the address assigning notification message 54. Avalue of the communication unit ID 52 added to the address acquiringrequest message 50 is substituted as the communication unit ID 56. Theassigned address 57 is the network address to be assigned to the childstation. The assigned period 58 is a period during which the networkaddress to be assigned to the child station can be used. The childstation, when using the same network address for a period exceeding theassigned period 58, transmits the address acquiring request message 50to the parent station and renews the network address.

[0087]FIG. 7 shows a data structure of an address assigning refusingmessage 60. The address assigning refusing message 60 is made up of amessage code 61, a communication unit ID 62, and a requested address 63.The message code 61 is a code to show that a message is the addressassigning refusing message 60. A value of the communication unit ID 52of the child station added to the address acquiring request message 50is substituted as the communication unit ID 62. The acquired address 53added to the address acquiring request message 50 is substituted as therequested address 63.

[0088]FIG. 8 shows a data structure or an address pool acquiring requestmessage 70. The address pool acquiring request message 70 is made up ofa message code 71, a communication unit ID 72, numbers of requestedaddresses 73, and a head address of an acquired pool 74. The messagecode 71 is a code to show that a message is the address pool acquiringrequest message 70. The communication unit ID 72 is the ID used touniquely identify the child station transmitting the address poolacquiring request message 70. The number of the network addresses thatis desired to be acquired is substituted as the number of the requestedaddresses 73. When the child station transmitting the address poolacquiring request message 70 has not yet acquired the address pool, “0”(zero) is substituted as the head address of acquired pool 74 and whenthe child station has already acquired the address pool, the headnetwork address of the address pool is substituted.

[0089]FIG. 9 shows a data structure of the address pool assigningnotification message 75. The address pool assigning notification message75 is made up of a message code 76, a communication unit ID 77, numbersof assigned addresses 18, a head address of assigned pool 79, andassigned period 80. The message code 76 is a code to show that a messageis the address pool assigning notification message 75. A value of thecommunication unit ID 72 added to the address pool acquiring requestmessage 70 is substituted as the communication unit ID 77. The numbersof assigned addresses 78 is the number of the network address to beassigned to the child station. The head address of the assigned pool 79is the head network address out of a plurality of consecutive networkaddresses to be assigned to the child station. A period during which theaddress pool to be assigned to the child station can be used issubstituted as the assigned period 80. The child station, when using thesame network address for a period exceeding the assigned period 80,transmits the address pool acquiring request message 70 to the parentstation and renews the address pool.

[0090]FIG. 10 shows a data structure of an address pool assigningrefusing message 81. The address pool assigning refusing message 81 ismade up of a message code 82, a communication unit ID 83, and a headaddress of requested pool 84. The message code 82 is a code to show thata message is the address pool assigning refusing message 81. A value ofthe communication unit ID 72 of the child station added to the addresspool acquiring request message 70 is substituted as the communicationunit ID 83. A value of the head address of acquired pool 74 added to theaddress pool acquiring request message 70 is substituted as the headaddress of requested pool 84.

[0091] A disconnection notifying message 86 is transmitted from theradio-relay station 2-i being the parent station to the child stationand is used to notify the child station that the communication betweenthe parent station and the wireless network system has becomeimpossible. A tree movement notifying message 88 is transmitted from theradio-relay station 2-i being the parent station to the child stationand is used to notify the child station that the connection of theparent station has moved to another wireless network system.

[0092] A private address is set to the network address for the wirelessnetwork system of the present invention, for example, 10.0.0.0/8 with ahigh-order one byte being fixed is set. The wireless network system isconstructed for every radio-relay terminating station 1. A high-ordersecond byte of the network address is used to identify each of thewireless network systems. For example, the private address, 10.1.0.0/16with its high-order second byte being fixed, is set to the wirelessnetwork system constructed of the radio-relay terminating station 1 andanother private address, 10.2.0.0/16 with its high-order second bytebeing fixed, is set to the wireless network system constructed ofanother radio-relay terminating station 1′.

[0093] The radio-relay terminating station 1 stores private addresses10.1.0.1/24 to 10.1.0.254/24 as the network addresses to be assigned tothe radio-relay station 2-i and private addresses 10.1.1.1/24 to10.1.254.254/24 as an address pool to be provided to the radio-relaystation 2-i. The address pool is a plurality of network addresses to beassigned by the radio-relay station 2-i to its child stations.

[0094] The radio-relay terminating station 1 assigns the address pool tothe radio-relay station 2-i. The number of the network addressesbelonging to the address pool is a fixed number. Because it is the fixednumber, work of the radio-relay terminating station 1 managing thenetwork address is made easy and work that the radio-relay station 2-iassigns the network address is made simple.

[0095] The radio-relay station 2-i acquires one network address out ofthe acquired address pool, assigns the acquired network address to theradio-relay station 2-i and uses it for communications with its childstation. The remaining network address contained in the address pool isassigned to each of the child stations. For example, if the number ofthe network addresses contained in the address pool is eight, thenetwork address having a remainder obtained by dividing the value of thenetwork addresses by eight being 1 (one) is assigned to the radio-relaystation and the network address having the remainder obtained bydividing the value of the network address by eight being not 1 (one) isassigned to its child station.

[0096] For example, when eight addresses 10.1.1.1/24 to 10.1.1.8/24 asthe address pool are assigned to the parent station, the addresses10.1.1.1/24 is assigned to the radio-relay station and the addresses10.1.1.2/24 to 10.1.1.8/24 are assigned to its child station. At thispoint, the network address of the parent station is a function of thenetwork address of the child station and the network address obtained bysubstituting 001 for low-order three bits of the network addressassigned to its child station is the network address of the parentstation of the child station. If the network address of the childstation is 10.1.1.2/24, the network address of its parent station is10.1.1.1/24.

[0097] When an operation of the radio-relay terminating station 1starts, the parent station processing section 8 in the radio-relayterminating station 1 transmits the wireless control signal message 30through the input/output section 7 intermittently to the child station.The parent station processing section 8, in response to theparticipation request message 34 fed from the child station, transmitsthe participation acknowledgment message 38 to the child station. Theaddress assigning section 5, in response to the address acquiringrequest message 50 fed from the child station, acquires the assignedaddress from the address managing table 4, describes the acquiredassigned address on the address assigning notification message 54 andtransmits it to the child station. When there is shortage of the networkaddress to be assigned, the address assigning section 5 transmits theaddress assigning refusing message 60 to refuse the request for thenetwork address from the child station.

[0098] The address pool assigning section 6 in the radio-relayterminating station 1, in response to the address pool acquiring requestmessage 70 fed from the child station, acquires the network addresscorresponding to the numbers of requested addresses 73 from the addressmanaging table 4, describes the acquired network address pool on theaddress pool assigning notification message 75 and notifies the childstation of it.

[0099]FIG. 11 to FIG. 14 are flowcharts explaining operations of theradio-relay station 2-i according to the embodiment of the presentinvention. When an operation of the radio-relay station 2-i starts, theoperational flow shown in the flowchart also commences. First, the childstation processing section 17-i in the radio-relay station 2-iretrieves, through the input/output section 11-i on the side of theparent station, the wireless control signal message 30 to be transmittedfrom the parent station (Step L1). Its parent is either of theradio-relay terminating station 1 or other radio-relay station 2-i.

[0100] The child station processing section 17-i, when having notreceived the wireless control signal message 30 to be transmitted fromthe parent station (Step L2; NO), repeats Step L1 and retrieves thewireless control signal message 30. The child station processing section17-i, when having received the wireless control signal message 30 (StepL2; YES), transmits, through the input/output section 11-i on the parentstation side, the participation request message 34 to the parent stationtransmitting the wireless control signal message 30 (Step L3)

[0101] The child station processing section 17-i retrieves, through theinput/output section 11-i on the side of the parent station, theparticipation acknowledgment message 38 to be transmitted from theparent station. It the child station processing section 17-i does notreceive the participation acknowledgment message 38 to be transmittedfrom the parent station (Step L4; NO), the child station processingsection 17-i repeats the retrieval of the participation acknowledgmentmessage 38. The child station processing section 17-i, when havingreceived the participation acknowledgment message 38 (Step L4; YES),transmits the address acquiring request message 50 to the parent stationhaving transmitted the participation acknowledgment message 38 (StepL5).

[0102] The address acquiring section 12-i, through the input/outputsection 11-i, retrieves the address assigning notfication message 54 tobe transmitted from the parent station. The address acquiring section12-i, when not receiving the address assigning notification message 54to be transmitted from the parent station (Step L6; NO), repeats theretrieval of the address assigning notification message 54.

[0103] The address acquiring section 12-i, when having received theaddress assigning notification message 54 (Step L6; YES), acquires theassigned address 57 from the address assigning notification message 54and stores the assigned address 57 (Step L7). The address pool acquiringsection 13-i transmits, through the input/output section 11-i on theside of the parent station, the address pool acquiring request message70 to the radio-relay terminating station 1 in the wireless networksystem to which the parent station belongs (step L8).

[0104] The radio-relay terminating station 1, in response to the addresspool acquiring request message 10, transmits the address pool assigningnotification message 75 to the radio-relay station 2-i. The address poolacquiring section 13-i, through the input/output section on the side ofthe parent station 11-i, retrieves the address pool assigningnotification message 75 to be transmitted from the radio-relayterminating station 1. The address pool acquiring section 13-i, when notreceiving the address pool assigning notification message 75 to betransmitted from the radio-relay terminating station 1 (Step L9; NO),repeats the retrieval of the address pool assigning notification message75.

[0105] The address pool acquiring section 13-i, when having received theaddress pool assigning notification message 75 (Step L9; YES), acquiresthe numbers of assigned addresses 78 from the address pool assigningnotification message 75 and the head address of assigned pool 79,produces a plurality of the network addresses and stores the pluralityof the network addresses on the address managing table 14-i (Stop L10).

[0106] The parent station processing section 18-i, through theinput/output section 16-i on the side of the child station, transmitsthe wireless control signal message 30 to the child station (Step L11).The child station is either of other radio-relay station 2-i″ or the wreless terminal 3-j. The child station, in response to the wirelesscontrol signal message 30, transmits the participation request message34 to the radio-relay station 2-i. The parent station processing section18-i, through the input/output section 16-i on the side of the childstation, retrieves the participation request message 34 to betransmitted from the child station.

[0107] The parent station processing section 18-i, when having receivedthe participation request message 34 (Step L12), transmits theparticipation acknowledgment message 38 to the child station which hastransmitted the participation request message 34 (Step L13). The childstation, in response to the participation acknowledgment message 38,transmits the address acquiring request message 50 to the radio-relaystation 2-i. The parent station processing section 18-i, when notreceiving the address acquiring request message 50 to be transmittedfrom the child station (Step L14; NO) ,repeats the retrieval of theaddress acquiring request message 50. The parent station processingsection 18-i, when having received the address acquiring request message50 (Step L14; YES), transmits the address assigning notification message54 to the child station which has transmitted the address acquiringrequest message 50 (Step L15).

[0108] The child station processing section 17-i, when the parentstation processing section 18-i has not received the participationrequest message 34 within a predetermined period of time (Step L12; NO)or after the parent station processing section 18-i has transmitted theaddress assigning notification message 54 to the child station, judgeswhether the communication with the parent station is possible or not(Step Ll6). When the communication with the parent station is possible(Step L16; YES), the procedure in Step L11 is again performed and theparent station processing section 18-i transmits the wireless controlsignal message 30 to the child station.

[0109] The child station processing section 17-i, when the communicationwith the parent station is impossible (Step L16; NO), through theinput/output section 11-i on the side of the parent station, retrievesthe wireless control signal message 30 to be transmitted from the otherparent station (Step L17). The other parent station is either of theradio-relay terminating station 1 or other radio-relay station 2-i′.

[0110] The child station processing section 17-i, when having receivedthe wireless control signal message 30 fed from the parent station (StepL18; YES), transmits the participation request message 34 to the parentstation transmitting the wireless control signal message 30 (Step L19).The parent station, in response to the participation request message 34,transmits the participation acknowledgment message 38 to the radio-relaystation 2-i. The child station processing section 17-i, through theinput/output section 11-i on the side of the parent stations retrievesthe participation acknowledgment message 38 to be fed from the parentstation. The child station processing section 17-i, when not receivingthe participation acknowledgment message 38 from the parent station(Step L20; NO), repeats the retrieval of the participationacknowledgment message 38.

[0111] When the child station processing section 17-i has received theparticipation acknowledgment message 38 (Step L20; YES), the addressacquiring section 12-i discards the stored network address (Step L21).The address acquiring section 12-i transmits the address acquiringrequest message 50 to the parent station that has fed the participationacknowledgment message 38 (Step L22). The parent station, in response tothe address acquiring request message 50, transmits the addressassigning notification message 54 to the radio-relay station 2-i.

[0112] The address acquiring section 12-i, retrieves the addressassigning notification message 54 to be fed from the parent station,through the input/output section 11-i on the side of the parent station.The address acquiring section 12-i, when not receiving the addressassigning notification message 54 to be fed from the parent station(Step L23; NO), repeats the retrieval of the address assigningnotification message 54.

[0113] The address acquiring section 12-i, when having received theaddress assigning notification message 54 (Step L23; YES), acquires theassigned address 57 from the address assigning notification message 54and stores the assigned address 57 (Step L24). The address acquiringsection 12-i judges whether the wireless network system to which theradio-relay station 2-i belonged last time is the same as that to whichthe radio-relay station 2-i belongs this time (Step L25).

[0114] The judgment in Step L25 is made by comparison between thenetwork address acquired last time and the network address acquired thistime. That is, by comparing a second high-order byte the networkaddress, each wireless network system is identified and whether thewireless network system to which the radio-relay station 2-i belongedlast time is the same as that to which the radio-relay station 2-ibelongs this time.

[0115] If the radio-relay station 2-i belongs to the network systembeing different from that to which the radio-relay station 2-i belongedlast time (Step L25; YES), the procedure in Step L16 is again performed.When the radio-relay station 2-i belongs to the same network to which itbelonged last time (Step L25; NO), the address pool acquiring section13-i discards the stored network address pool (Step L26). The addresspool acquiring section 13-i, through the input/output section 11-i onthe side of the parent station, transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1′ in thewireless network system to which the parent station belongs (Step L27).

[0116] The radio-relay terminating station 1′ in response to the addresspool acquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-i. The address poolacquiring section 13-i, through the input/output section 11-i on theside of the parent station, retrieves the address pool assigningnotification message 75 to be fed from the radio-relay terminatingstation 1′. The address pool acquiring section 13-i, when not receivingthe address pool assigning notification message 75 to be fed from theradio-relay terminating station 1′ (Step L28; NO), repeats the retrievalof the address pool assigning notification message 75.

[0117] The address pool acquiring section 13-i, when having received theaddress pool assigning notification message 75 (Step L28; YES), acquiresthe numbers of the assigned addresses 78 and the head address ofassigned pool 79 from the address pool assigning notification message75, produces a plurality of addresses and stores the plurality of theaddresses in the address managing table 14-i. The parent stationprocessing section 18-i transmits the tree movement notifying message 88(Step L29). The network address is again assigned to all the childstations.

[0118] When the child station processing section 17-i has not receivedthe wireless control signal message 30 to be fed from the parent station(Step L18; NO), discards the stored network address (Step L30) and theaddress pool acquiring section 13-i discards the stored network addresspool (Step L31). The parent station processing section 18-i transmits adisconnection notification message 86 to all the child stationsconnected to the radio-relay station 2-i (Step L32).

[0119] When operations of the wireless terminal 3-j are started, thechild station processing section 23-j retrieves the wireless controlsignal message 30 to be fed from the parent station, through theinput/output section 21-j. The child station processing section 23-j,when having received the wireless control signal message 30 to be fedfrom the parent station, transmits the participation request message 34,through the input/output section 21-j, to the parent station.

[0120] The address acquiring section 22-j transmits the addressacquiring request message 50 through the input/output section 21-j tothe parent station. The address acquiring section 22-j, when havingreceived the address assigning notification message 54 from the parentstation, acquires the assigned address 57 from the address assigningnotification message 54 and stores the assigned address 57.

[0121] When the communication with the parent station is madeimpossible, the child station processing section 23-j retrieves thewireless control signal message 30 to be fed from other parent station.The child station processing section 23-j, when having received thewireless control signal message 30 from the parent station, transmits,through the input/output section 21-j, the participation request message34 to the parent station. The address acquiring section 22-j discardsthe stored network address and transmits the address acquiring requestmessage 50 to the parent station.

[0122]FIG. 15 and 16 are diagrams showing sequences of operationsrequired to newly construct the wireless network system. Of thecommunication devices making up the wireless network system, theradio-relay terminating station 1 is first booted. At this point, to theaddress managing table 4 in the radio-relay terminating station 1 arcset the network addresses that can be initially used. The parent stationprocessing section 8 in the radio-relay terminating station 1 transmitsthe wireless control signal message 30 intermittently to the childstation through the input/output section 7.

[0123] When operations of the radio-relay station 2-1 start, the childstation processing section 17-1 in the radio-relay station 2-1retrieves, through the input/output section 11-1 on the side ot theparent station, the wireless control signal message 30 to be fed fromthe radio-relay terminating station 1. The child station processingsection 17-1, in response to the wireless control signal message 30,transmits the participation request message 34 to the radio-relayterminating station 1 (Step S1) to request that the radio-relay station2-1 becomes the child station of the radio-relay terminating station 1.

[0124] The parent station processing section 8 in the radio-relayterminating station 1 receives the participation request message 34 fromthe radio-relay station 2-1 through the input/output section 7. Theparent station processing section 8, if it allows the network system toparticipate, transmits the participation acknowledgment message 38 tothe radio-relay station 2-1 (Step S2). The child station processingsection 17-1 in the radio-relay station 2-1 receives the participationacknowledgment message 38. By such exchange of messages, the radio-relayterminating station 1 serving as the parent station can carry outcommunications with the radio-relay station 2-1 serving as the childstation.

[0125] The address acquiring section 12-1 transmits the addressacquiring request message 50 to the radio-relay terminating station 1 tomake a request for the network address (Step S3). The address assigningsection 5 of the radio-relay terminating station 1, in response to theaddress acquiring request message 50, acquires the assigned address fromthe address managing table 4, describes the acquired assigned address onthe address assigning notification message 54 and transmits it to theradio-relay station 2-1 (Step S4). When there is shortage of the networkaddress to be assigned, the radio-relay terminating station 1 transmitsthe address assigning refusing message 60 to refuse the request for thenetwork address from the child station.

[0126] The address acquiring section 12-1 in the radio-relay station 2-1receives the address assigning notification message 54. The addressacquiring section 12-1 acquires the assigned address 57 from the addressassigning notification message 54 and stores it. The address poolacquiring section 13-1 in the radio-relay station 2-1 transmits theaddress pool acquiring request message 70 to the radio-relay terminatingstation 1 (Step S5).

[0127] The address pool assigning section 6 in the radio-relayterminating station 1 receives the address pool acquiring requestmessage 70 from the radio-relay station 2-1. The address pool assigningsection 6 acquires the network address corresponding to numbers ofrequested addresses 73 from the address managing table 4, describes theacquired network address pool on the address pool assigning notificationmessage 75 and notifies the radio-relay station 2-1 of it (Step S6).

[0128] The radio-relay terminating station 1, if it refuses the addresspool acquiring request message 70 due to shortages in the networkaddress pool to be assigned or a like, transmits the address poolassigning refusing message 81.

[0129] The address pool acquiring section 13-1 in the radio-relaystation 2-1, in response to the address pool assigning notificationmessage 75, acquires the assigned address pool from the address poolassigning notification message 75 and stores the assigned address poolin the address managing table 14-1. The parent station processingsection 18-1 in the radio-relay station 2-1 transmits the wirelesscontrol signal message 30 to the child station over a wireless channelbeing different from the wireless channel being used by the radio-relayterminating station 1.

[0130] Next, when operations of the radio-relay station 2-2 start, thesame processing as performed on the radio-relay station 2-1 is performed(Step S1 to S6) That is, when operations of the radio-relay station 2-2start, the child station processing section 17-2 in the radio-relaystation 2-2 retrieves the wireless control signal message 30 to be fedfrom the parent station through the input/output section 11-2 on theside of the parent station. The child station processing section 17-2,in response to the wireless control signal message 30 to be fed from theradio-relay terminating station 1, transmits the participation requestmessage 34 to the radio-relay terminating station 1 (Step S7) andrequests that the radio-relay station 2-2 becomes the child station ofthe radio-relay terminating station 1.

[0131] The parent station processing section 8 in the radio-relayterminating station 1 receives the participation request message 34 fromthe radio-relay station 2-2 through the input/output section 7. Theparent station processing section 8, if it allows the participation ofthe network system, transmits the participation acknowledgment message38 to the radio-relay station 2-2 (Step S8). The child stationprocessing section 17-2 in the radio-relay station 2-2 receives theparticipation acknowledgment message 38. By such exchange of messages,the radio-relay terminating station 1 serving as the parent station cancarry out communications with the radio-relay station 2-2 serving as thechild station.

[0132] The address acquiring section 12-2 transmits the addressacquiring request message 50 to the radio-relay terminating station 1and makes a request for the acquisition of the network address (StepS9). The address assigning section 5 in the radio-relay terminatingstation 1, in response to the address acquiring request message 50,acquires the assigned address from the address managing table 4,describes the acquired address on the address assigning notificationmessage 54 and transmits it to the radio-relay station 2-2 (Step S10)When there is shortage of the network address to be assigned, theradio-relay terminating station 1 transmits the address assigningrefusing message 60 to refuse the request for the network address fromthe radio-relay station 2-2.

[0133] The address acquiring section 12-2 in the radio-relay station 2-2receives the address assigning notification message 54. The addressacquiring section 12-2 acquires the assigned address 57 from the addressassigning notification message 54 and stores it. The address poolacquiring section 13-2 in the radio-relay station 2-2 transmits theaddress pool acquiring request message 70 to the radio-relay terminatingstation 1 (Step S11).

[0134] The address pool assigning section 6 in the radio-relayterminating station 1 receives the address pool acquiring requestmessage 70 from the radio-relay station 2-2. The address pool assigningsection 6 acquires the network address corresponding to numbers ofrequested addresses 73 from the address managing table 4 and describesthe acquired network address pool on the address assigning notificationmessage 75 and notifies the radio-relay station 2-2 of it (Step S12).

[0135] The address pool acquiring section 13-2 in the radio-relaystation 2-2, in response to the address pool assigning notificationmessage 75, acquires the address pool assigned from the address poolassigning notification message 75 and stores the assigned address poolin the address managing table 14-2. The parent station processingsection 18-2 in the radio-relay station 2-2 transmits the wirelesscontrol signal message 30 to the child station over the wireless channelbeing different from that used in the radio-relay terminating station 1.

[0136] When operations of the wireless terminal 3-1 start, the childstation processing section 23-1 retrieves the wireless control signalmessage 30 to be transmitted from the parent station. The child stationprocessing section 23-1, in response to the wireless control signalmessage 30 to be fed from the radio-relay station 2-1, transmits theparticipation request message 34 to the radio-relay station 2-1 (StepS13) and requests that the radio-relay station 2-1 becomes the childstation of the radio-relay terminating station 1.

[0137] The parent station processing section 18-1 in the radio-relaystation 2-1 receives the participation request message 34 from thewireless terminal 3-1. The parent station processing section 18-1, if itallows the participation of the network system, transmits theparticipation acknowledgment message 38 to the wireless terminal 3-1(Step S14). The child station processing section 23-1 in the wirelessterminal 3-1 receives the participation acknowledgment message 38. Bysuch exchange of messages, the radio-relay station 2-1 serving as theparent station can carry out communications with the wireless terminal3-1 serving as the child station.

[0138] The address acquiring section 22-1 transmits the addressacquiring request message 50 to the radio-relay station 2-1 to make arequest for acquisition of the network address (Step S15). The addressassigning section 15-1 in the radio-relay station 2-1, in response tothe address acquiring request message 50, acquires the assigned addressfrom the address managing table 14-1, describes the acquired assignedaddress on the address assigning notification message 54 and notifiesthe wireless terminal 31 of it (Step S16). When there is shortage of thenetwork address to be assigned, the radio-relay station 2-1 transmitsthe address assigning refusing message 60 to refuse the request for thenetwork address from the wireless terminal 3-1.

[0139] The address acquiring section 22-1 in the wireless terminal 3-1,when having received the address assigning notification message 54 fromthe radio-relay station 2-1, acquires the assigned address 57 from theaddress assigning notification message 54 and stores it.

[0140] When operations of the wireless terminal 3-2 start, the sameprocessing as performed on the wireless terminal 3-1 is performed (StepS13 to S16). That is, when operations of the wireless terminal 3-2start, the child station processing section 23-2 retrieves the wirelesscontrol signal message 30 to be fed from the parent station. The childstation processing section 23-2, in response to the wireless controlsignal message 30 to be fed from the radio-relay station 2-2, transmitsthe participation request message 34 to the radio-relay station 2-2(Step S17) and requests that the radio-relay station 2-2 becomes thechild station of the radio-relay terminating station 1.

[0141] The parent station processing section 18-2 in the radio-relaystation 2-2 receives the participation request message 34 front thewireless terminal 3-2. The parent station processing section 18-2, if itallows the participation of the network system, transmits theparticipation acknowledgment message 38 to the wireless terminal 3-2(Step S18). The child station processing section 23-2 in the wirelessterminal 3-2 receives the participation acknowledgment message 38. Bysuch exchange of messages, the radio-relay station 2-2 serving as theparent station can carry out communications with the wireless terminal3-2 serving as the child station.

[0142] The address acquiring section 22-2 transmits the addressacquiring request message 50 to the radio-relay station 2-2 to make arequest for acquisition of the network address (Step S19) The addressassigning section 15-2 in the radio-relay station 2-2, in response tothe address acquiring request message 50, acquires the assigned addressfrom the address managing table 14-2, describes the acquired assignedaddress on the address assigning notification message 54 and notifiesthe wireless terminal 3-2 of it (Step S20). The address acquiringsection 22-2 in the wireless terminal 3-2, when having received theaddress assigning notification message 54 from the radio-relay station2-2, acquires the assigned address 57 from the address assigningnotification message 54 and stores it.

[0143]FIG. 17 is a schematic block diagram showing another example ofthe wireless network system according to the embodiment of the presentinvention. The radio-relay terminating station 1 is connected to theradio-relay station 2-3 and to the radio-relay station 2-4. Theradio-relay station 2-3 is connected to the radio-relay station 2-5 andto the radio-relay station 26. The radio-relay station 2-4 is connectedto the radio-relay station 2-7. The radio-relay station 2-5 is connectedto the wireless terminal 3-3 and to the wireless terminal 3-4. Theradio-relay station 2-6 is connected to the wireless terminal 3-5. Theradio-relay station 2-7 is connected to the wireless terminal 3-6.

[0144]FIGS. 18 and 19 are diagrams showing operations performed whencommunication between the radio-relay station 2-3 and the radio-relaystation 2-6 becomes impossible. The radio-relay station 2-3, in responseto the wireless control signal message 30 transmitted from theradio-relay terminating station 1, transmits the participation requestmessage 34 to the radio-relay terminating station 1 (Step S30). Theradio-relay terminating station 1, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-3 (Step S31). By such exchange ofmessages, the radio-relay terminating station 1 serving as the parentstation can carry out communications with the radio-relay station 2-3serving as the child station.

[0145] The radio-relay station 2-3 transmits the address acquiringrequest message 50 to the radio-relay terminating station 1 (Step S32).The radio-relay terminating station 1, in response to the addressacquiring request message 50, transmits the address assigningnotification message 54 to the radio-relay station 2-3 (Step S33). Theradio-relay station 2-3 receives the address assigning notificationmessage 54 and acquires its network address.

[0146] The radio-relay station 2-3 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S34).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-3 (Step S35). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits, as the parentstation, the wireless control signal message 30 over a wireless channelbeing different from that used by the radio-relay terminating station 1.

[0147] When operations of the radio-relay station 2-2 start, the sameprocessing as performed on the radio-relay station 2-3 is performed(Step S30 to S35). That is, the radio-relay station 2-4, in response tothe wireless control signal message 30 fed from the radio-relayterminating station 1, transmits the participation request message 34 tothe radio-relay terminating station 1 (Step S36). The radio-relayterminating station 1, in response to the participation requests message34, transmits the participation acknowledgment message 38 to theradio-relay station 2-4 (Step S37). By such exchange of messages, theradio-relay terminating station 1 serving as the parent station cancarry out communications with the radio-relay station 2-4 serving as thechild station.

[0148] The radio-relay station 2-4 transmits the address acquiringrequest message 50 to the radio-relay terminating station 1 (Step S38).The radio-relay terminating station 1, in response to the addressacquiring request message 50, transmits the address assigningnotification message 54 to the radio-relay station 2-4 (Step S39). Theradio-relay station 2-4 receives the address assigning notificationmessage 54 and acquires its network address.

[0149] The radio-relay station 2-4 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S40).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-4 (Step S41). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits, as the parentstation, the wireless control signal message 30 over the wirelesschannel being different from that used in the radio-relay terminatingstation 1.

[0150] The radio-relay station 2-6, in response to the wireless controlsignal message 30 fed from the radio-relay station 2-3, transmits theparticipation request message 34 to the radio-relay station 2-3 (StepS42). The radio-relay station 2-3, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-6 (Step S43). By such exchange ofmessages, the radio-relay station 2-3 serving as the parent station cancarry out communications with the radio-relay station 2-6 serving as thechild station.

[0151] The radio-relay station 2-6 transmits the address acquiringrequest message 50 to the radio-relay station 2-3 (Step S44). Theradio-relay station 2-3, in response to the address acquiring requestmessage 50, transmits the address assigning notification message 54 tothe radio-relay station 2-6 (Step S45). The radio-relay station 2-6receives the address assigning notification message 54 and acquires itsnetwork address.

[0152] The radio-relay station 2-6 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S46).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-6 (Step S47). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits the wireless controlsignal message 30 over a wireless channel being different from that usedin the radio-relay terminating station 1.

[0153] At this point, when the radio-relay station 2-6 cannot carry outcommunication with the radio-relay station 2-3, the radio-relay station2-6 again retrieves the wireless control signal message 30. Theradio-relay station 2-6, in response to the wireless control signalmessage 30 fed from the radio-relay station 2-4, transmits theparticipation request message 34 to the radio-relay station 2-4 (StepS48). The radio-relay station 2-4, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-6 (Step S49). By such exchange ofmessages, the radio-relay station 2-4 serving as the parent station cancarry out communications with the radio-relay station 2-6 serving as thechild station.

[0154] The radio-relay station 2-6 transmits the address acquiringrequest message 50 to the radio-relay station 2-4 (Step S50). Theradio-relay station 2-4, in response to the address acquiring requestmessage 50, transmits the address assigning notification message 54 tothe radio-relay station 2-6 (Step S51). The radio-relay station 2-6receives the address assigning notification message 54 and acquires itsnetwork address.

[0155] The radio-relay station 2-6 compares the network address newlyassigned with the network address assigned before and judges whether thewireless network system to which the radio-relay station 2-6 belongedbefore is the same as, or is different from, the wireless network systemto which the radio-relay station 2-6 belongs this time. Such thejudgment is carried out by comparing high-order two bytes of the twonetwork addresses and, if its high-order two bytes match with eachother, the two wireless network systems are judged to be the same and,if its high-order two bytes do not match with each other, the twowireless network systems are judged to be different from each other.

[0156] When the wireless network systems are the same, since theradio-relay station 2-6 has already acquired the address pool obtainedfrom the radio-relay terminating station 1, it is not necessary toacquire the address pool from the radio-relay terminating station 1. Asa result, the traffic between the radio-relay station 2-6 and theradio-relay terminating station does not increase.

[0157]FIGS. 20 and 21 are diagrams showing operations performed whencommunication between the radio-relay station 2-3 and the wirelessterminal 3-5 of the embodiment become impossible. The radio-relaystation 2-3, in response to the wireless control signal message 30 fedfrom the radio-relay terminating station 1, transmits the participationrequest message 34 to the radio-relay terminating station 1 (Step S60).The radio-relay terminating station 1, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-3 (Step S61). By such exchange ofmessages, the radio-relay terminating station 1 serving as the parentstation can carry out communications with the radio-relay station 2-3serving as the child station.

[0158] The radio-relay station 2-3 transmits the address acquiringrequest message 50 to the radio-relay terminating station 1 (Step 562).The radio-relay terminating station 1, in response to the addressacquiring request message 50, transmits the address assigningnotification message 54 to the radio-relay station 2-3 (Step S63). Theradio-relay station 2-3 receives the address assigning notificationmessage 54 and acquires its network address.

[0159] The radio-relay station 2-3 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S64).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-3 (Step S65). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits the wireless controlsignal message 30 over a wireless channel being different from that usedin the radio-relay terminating station 1.

[0160] The radio-relay station 2-6, in response to the wireless controlsignal message 30 fed from the radio-relay station 2-3, transmits theparticipation request message 34 to the radio-relay station 2-3 (StepS66). The radio-relay station 2-3, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-6 (Step S67). By such exchange ofmessages, the radio-relay station 2-3 serving as the parent station cancarry out communications with the radio-relay station 2-6 serving as thechild station.

[0161] The radio-relay station 2-6 transmits the address pool acquiringrequest message 70 to the radio-relay station 2-3 (Step S68). Theradio-relay station 2-3, in response to the address pool acquiringrequest message 70, transmits the address assigning notification message54 to the radio-relay station 2-6 (Step S69) The radio-relay station 2-6receives the address assigning notification message 54 and acquires itsnetwork address.

[0162] The radio-relay station 2-6 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S70).

[0163] The radio-relay terminating station 1, in response to the addresspool acquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-6 (Step S71). Theradio-relay station 2-6 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits, as the parentstation, the wireless control signal message 30 over a wireless channelbeing different from that used in the radio-relay terminating station 1.

[0164] The wireless terminal 3-5, in response to the wireless controlsignal message 30 fed from the radio-relay station 26, transmits theparticipation request message 34 to the radio-relay station 2-6 (StepS72). The radio-relay station 2-6, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the wireless terminal 3-5 (Step S73). By such exchange ofmessages, the radio-relay station 2-6 serving as the parent station cancarry out communications with the wireless terminal 3-5 serving as thechild station.

[0165] The wireless terminal 3-5 transmits the address acquiring requestmessage 50 to the radio-relay station 2-6 (Step S74). The radio-relaystation 2-6, in response to the address acquiring request message 50,transmits the address assigning notification message 54 to the wirelessterminal 3-5 (Step S75). The wireless terminal 3-5 receives the addressassigning notification message 54 and acquires its network address.

[0166] At this point, when the radio-relay station 2-6 cannot carry outcommunication with the radio-relay station 2-3, the radio-relay station2-6 again retrieves the wireless control signal message 30. Theradio-relay station 2-6, when being unable to find the parent station,transmits the disconnection notifying message 86 to the wirelessterminal 3-5 (Step S76). The wireless terminal 3-5, in response to thedisconnection notifying message 86, discards the assigned networkaddress and again searches for the parent station.

[0167] Moreover, the radio-relay station 2-1, when having received thedisconnection notification message 76, discards the network addressassigned to the radio-relay station 2-1, transmits the disconnectionnotifying message 86 to the child station, discards the address poolassigned to the radio-relay station 2-1 and again searches for theparent station. When the address assigned period 80 of the discardedaddress pool expires, the radio-relay terminating station 1 re-uses theaddress pool to assign it to the child parent.

[0168] By the transmission of such the disconnection notifying message86, the child station recognizes that it cannot carry out communicationswith the radio-relay station and can search for another parent stationpromptly and smoothly. Since the address pool has the address assignedperiod 80, when the radio-relay station cannot carry out communicationswith the radio-relay station, the network address that is not used canbe assigned to another radio-relay station.

[0169]FIG. 22 is a block diagram showing still another example of thewireless network system according to the embodiment of the presentinvention. The radio-relay terminating station 1 is connected to theradio-relay station 2-3 and to the radio-relay station 2-4. Theradio-relay station 2-3 is connected to the radio-relay station 2-5 andto the radio-relay station 2-6. The radio-relay station 2-4 is connectedto the radio-relay station 2-7. The radio-relay station 2-5 is connectedto the wireless terminal 3-3 and to the wireless terminal 3-4. Theradio-relay station 2-6 is connected to the wireless terminal 3-6. Theradio-relay station 2-7 is connected to the wireless terminal 3-6.

[0170] The radio-relay terminating station 1′ is connected to theradio-relay station 2-8 and to the radio-relay station 2-9. Theradio-relay station 2-8 is connected to the radio-relay station 2-10.The radio-relay station 2-9 is connected to the radio-relay station2-11. The radio-relay station 2-10 is connected to the wireless terminal3-7. The radio-relay station 2-11 is connected to the wireless terminal3-8.

[0171] In the wireless network system made up of the radio-relayterminating station 1, a network address 10.1.0.0/16 with high-order twobytes being fixed is set. In the wireless network system made up of theradio-relay terminating station 1′, a network address 10.2.0.0/16 withhigh-order two bytes being fixed is set.

[0172]FIGS. 23 and 24 are diagrams showing operations performed whencommunication between the radio-relay stations 2-4 and the radio-relaystation 2-7 of she embodiment becomes impossible. The radio-relaystation 2-4, at an initial stage, in response to the wireless controlsignal message 30 fed from the radio-relay terminating station 1,transmits the participation request message 34 to the radio-relayterminating station 1 (Step S100). The radio-relay terminating station1, in response to the participation request message 34, transmits theparticipation acknowledgment message 38 to the radio-relay station 2-4(Step S101). By such exchange of messages, the radio-relay terminatingstation 1 serving as the parent station can carry out communicationswith the radio-relay station 2-4 serving as the child station.

[0173] The radio-relay station 2-4 transmits the address acquiringrequest message 50 to the radio-relay terminating station 1 (Step S102).The radio-relay terminating station 1, in response to the addressacquiring request message 50, transmits the address assigningnotification message 54 to the radio-relay station 2-4 (Step S103). Theradio-relay station 2-4 receives the address assigning notificationmessage 54 and acquires its network address.

[0174] The radio-relay station 2-4 transmits the address pool acquiringrequest message 10 to the radio-relay terminating station 1 (Step S104).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-4 (Step S105). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits, as the parentstation, the wireless control signal message 30 over a wireless channelbeing different from that used in the radio-relay terminating station 1.

[0175] The radio-relay station 2-8, in response to the wireless controlsignal message 30 ted from the radio-relay terminating station 1′,transmits the participation request message 34 to the radio-relayterminating station 1′ (Step S106). The radio-relay terminating station1′, in response to the participation request message 34, transmits theparticipation acknowledgment message 38 to the radio-relay station 2-8(Step S107). By such exchange of messages, the radio-relay terminatingstation 1′ serving as the parent station can carry out communicationswith tho radio-relay station 2-8 serving as the child station.

[0176] The radio-relay station 2-8 transmits the address acquiringrequest message 50 to the radio-relay terminating station 1′ (StepS108). The radio-relay terminating station 1′, in response to theaddress acquiring request message 50, transmits the address assigningnotification message 54 to the radio-relay station 2-8 (Step S109). Theradio-relay station 2-8 receives the address assigning notificationmessage 54 and acquires its network address.

[0177] The radio-relay station 2-8 transmits the address pool acquiringrequest message 7O to the radio-relay terminating station 1′ (StepS110). The radio-relay terminating station 1′, in response to theaddress pool acquiring request message 70, transmits the address poolassigning notification message 75 to the radio-relay station 2-8 (StepS111). The radio-relay station 2-1 receives the address pool assigningnotification message 75, acquires the address pool and transmits, as theparent station, the wireless control signal message 30 over a wirelesschannel being different from that used in the radio-relay terminatingstation 1′.

[0178] The radio-relay station 2-7, in response to the wireless controlsignal message 30 fed from the radio-relay station 24, transmits theparticipation request message 34 to the radio-relay station 2-4 (StepS112) The radio-relay station 2-4, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the radio-relay station 2-7 (Step S113). By such exchange ofmessages, the radio-relay station 2-4 serving as the parent station cancarry out communications with the radio-relay station 2-1 serving as thechild station.

[0179] The radio-relay station 2-7 transmits the address acquiringrequest message 50 to the radio-relay station 2-4 (Step S114). Theradio-relay station 2-4, in response to the address acquiring requestmessage 50, transmits the address assigning notification message 54 tothe radio-relay station 2-7 (Step S115). The radio-relay station 2-7receives the address assigning notification message 54 and acquires itsnetwork address.

[0180] The radio-relay station 2-7 transmits the address pool acquiringrequest message 70 to the radio-relay terminating station 1 (Step S116).The radio-relay terminating station 1, in response to the address poolacquiring request message 70, transmits the address pool assigningnotification message 75 to the radio-relay station 2-7 (Step S117). Theradio-relay station 2-1 receives the address pool assigning notificationmessage 75, acquires the address pool and transmits, is the parentstation, the wireless control signal message 30 over a wireless channelbeing different from that used in the radio-relay terminating station 1.

[0181] The wireless terminal 3-6, in response to the wireless controlsignal message 30 fed from the radio-relay station 27, transmits theparticipation request message 34 to the radio-relay station 2-7 (StepS118). The radio-relay station 2-7, in response to the participationrequest message 34, transmits the participation acknowledgment message38 to the wireless terminal 3-6 (Step S119). By such exchange ofmessages, the radio-relay station 2-7 serving as the parent station cancarry out communications with the wireless terminal 3-6 serving as thechild station.

[0182] The wireless terminal 3-6 transmits the address acquiring requestmessage 50 to the radio-relay station 2-7 (Step S120). The radio-relaystation 2-7, in response to the address acquiring request message 50,transmits the address assigning notification message 54 to the wirelessterminal 3-6 (Step S121). The wireless terminal 3-6 receives the addressassigning notification message 54 and acquires its network address.

[0183] At this point, when the radio-relay station 2-7 cannot carry outcommunications with the radio-relay station 2-4, the radio-relay station2-7 again retrieves the wireless control signal message 30. Theradio-relay station 2-7, when having received the wireless controlsignal message 30 fed from the radio-relay station 2-8, transmits theparticipation request message 34 to the radio-relay station 2-8 (StepS122). The radio-relay station 2-8, in response to the participationrequest message 34 fed from the radio-relay station 2-7, transmits theparticipation acknowledgment message 38 to the radio-relay station 2-7(Step S123). By such exchange of messages, the radio-relay station 2-8serving as the parent station can carry out communications with theradio-relay station 2-7 serving as the child station.

[0184] The radio-relay station 2-7 transmits the address acquiringrequest message 50 to the radio-relay station 2-8 (Step S124). Theradio-relay station 2-8, in response to the address acquiring requestmessage 50 fed from the radio-relay station 2-7, transmits the addressassigning notification message 54 to the radio-relay station 2-7 (StepS125). The radio-relay station 2-7 receives the address assigningnotification message 54 fed from the radio-relay station 2-8 andacquires its network address.

[0185] The radio-relay station 2-7, by comparing the network addressassigned newly with the network address assigned before, judges whetherthe wireless network system to which the radio-relay station 2-7belonged before is the same as or different from the wireless networksystem to which the radio-relay station 2-7 belongs this time. When thewireless network system is different, the radio-relay station 2-7 makesa request of the radio-relay station making up the wireless networksystem for the address pool. That is, the radio-relay station 2-7transmits the address pool acquiring request message 70 to theradio-relay terminating station 1′ (Step S126)

[0186] The radio-relay terminating station 1′, in response to theaddress pool acquiring request message 70, transmits the addressassigning notification message 75 to the radio-relay station 2-7 (StepS127). The radio-relay station 2-1 receives the address pool assigningnotification message 75, acquires the address pool and transmits thetree movement notifying message 88 to all the child stations (StepS128).

[0187] The wireless terminal 3-6, in response to the tree movementnotifying message 88 fed from the radio-relay station 2-7, discards thenetwork address assigned to the radio-relay station 2-7 and transmitsthe address acquiring request message 50 to the radio-relay station 2-7(Step S129). The radio-relay station 2-7, in response to the addressacquiring request message 50 fed from the wireless terminal 3-6,transmits the address assigning notification message 54 to the wirelessterminal 3-6 (Step S130).

[0188] The radio-relay station 2-i, when having received the treemovement notifying message 88, discards the network address assigned tothe radio-relay station 2-i, transmits the address acquiring requestmessage 50 to the parent station to acquire the network address. Theradio-relay station 2-i further transmits the movement notifying message80 to the child station, discards the address pool assigned to theradio-relay station, transmits the address pool acquiring requestmessage 70 to the radio-relay terminating station 1′ to acquire theaddress pool again.

[0189] It is apparent that the present invention is not limited to theabove embodiments but may be changed and modified without departing fromthe scope and spirit of the invention.

What is claimed is:
 1. A wireless network system comprising: aradio-relay terminating station; a radio-relay station being connectedto said radio-relay terminating station in a wireless manner, a wirelessterminal being connected to said radio-relay station in a wirelessmanner; and wherein said radio-relay terminating station preserves aplurality of network addresses to be assigned to said radio-relaystation and to said wireless terminal, assigns a first network addressbelonging to said plurality of network addresses to said radio-relaystation and collectively feeds an address pool making up a part of saidplurality of network addresses to the radio-relay station and whereinsaid radio-relay station preserves said address pool and assigns asecond network address belonging to said address pool to said wirelessterminal.
 2. The wireless network system according to claim 1, furthercomprising an other radio-relay station, wherein said other radio-relaystation preserves an other address pool being different from saidaddress pool and wherein, when said radio-relay station is connected tosaid other radio-relay station, said other radio-relay station assigns athird network address belonging to said other address pool to saidradio-relay station.
 3. The wireless network system according to claim2, wherein, when said other radio-relay station is connected to saidradio-relay terminating station, said other address pool makes up of apart of said plurality of network addresses and said address pool is notrenewed and said second network address is not renewed.
 4. The wirelessnetwork system according to claim 2, further comprising an otherradio-relay terminating station which preserves an other plurality ofnetwork addresses being different from said plurality of networkaddresses and wherein, when said other radio-relay station is connectedto said other radio-relay terminating station, said address pool isrenewed to become still an other address pool making up a part of saidother plurality of network addresses and said second network address isrenewed to become a fourth network address belonging to said otheraddress pool.
 5. A network address assigning method for assigning anetwork address to a radio-relay station and a wireless terminal in awireless network system made up of a radio-relay terminating station,said radio-relay station, and said wireless terminal, said methodcomprising: a step of feeding a plurality of network addresses to saidradio-relay terminating station; a step of assigning a first networkaddress belonging to said plurality of network addresses to saidradio-relay station being connected to said radio-relay terminatingstation in a wireless manner; a step of notifying said radio-relaystation being connected to said radio-relay terminating station in saidwireless manner of an address pool making up a part of said plurality ofnetwork addresses; and a step of assigning a second network addressbelonging to said address pool to said wireless terminal being connectedto said radio-relay station in a wireless manner.
 6. The network addressassigning method according to claim 5, wherein said wireless networksystem includes an other radio-relay station having an other addresspool being different from said address pool and wherein, saidradio-relay station is connected to said other radio-relay station, athird network address belonging to said other address pool is assignedto said radio-relay station.
 7. The network address assigning methodaccording to claim 6, wherein, when said other radio-relay station isconnected to said radio-relay terminating station, said other addresspool makes up said plurality of network addresses and said address poolis not renewed and said third network address is not renewed.
 8. Thenetwork address assigning method according to claim 6, wherein saidwireless network system includes an other radio-relay terminatingstation and wherein, when said other radio-relay station is connected tosaid other radio-relay terminating station, said network addressassigning method comprises: a step of feeding an other plurality ofnetwork addresses being different from said plurality of networkaddresses to said other radio-relay terminating station; a step ofnotifying said other radio-relay station of said other address poolmaking up a part of said other plurality of network addresses; a step ofnotifying said radio-relay station of still an other address pool makingup a part of said other plurality of network addresses; and a step ofassigning a fourth network address belonging to still an other addresspool to said wireless terminal.
 9. The network address assigning methodaccording to claim 8, wherein each of said plurality of networkaddresses contains a value corresponding to said radio-relay terminatingstation and wherein, when said value belonging to said first networkaddress is different from said value belonging to said third networkaddress, still said other address pool is notified.